Electrical protective device.



B. H. SMITH.

ELECTRICAL PROTECTIVE DEVlCE.

AQPLICATION FILED JULY 1 I. 1914.

1 04,508. Patented Nov. 14, 1916.

WITNESSES: INVENTOR 4 (1,14 g 5 0?, {NM W ATTORNEY 'UNITED STAT ESPATENT OFFICE.

BENJAMIN H. SMITH, OF TUE'ILE CREEK, PENNSYLVANIA, ASSIGNOR TO WESTING-HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PEN N SYL-VANIA.

ELECTRICAL PROTECTIVE DEVICE.

\ I Specification of Letters Patent.

Patented Nov. 14, 1916.

Application filed July 11, 1914. Serial N 0. 850,331.

To all whom it may concern Be it known that I, BENJAMIN H. SMITH, acitizen of the United States, and a resident of Turtle Creek, in thecounty of Allegheny and State of Pennsylvania, have invented a new anduseful Improvement in Electrical Protective Devices, of which thefollowing is a specification.

My invention relates to electrical protective devices and. particularlyto relay mechanisms and systems that are employed for tripping circuitbreakers, or operating other devices, upon the occurrence ofpredetermined circuit conditions.

The object of my invention is to provide a simple and economical relaymechanism of the character indicated that may be operated by currentderived from the line or circuit in connection with which the circuitbreaker or other device is employed, there by obviating. the necessityof employing a separate source of power for supplying the operatingcurrent, and the contact members of which shall not be subjected toinjurious arcing, or to the possibility of welding or sticking together,or of becoming burned so that they will not conduct current.

Considerable difficulty has heretofore been experienced with relaymechanisms for circuit breakers and similar devices, that are employedin connection with alternating current circuits, when it has beenattempted to derive the current for tripping or operating the breakersfrom the said circuits. This difficulty has been due to the fact thatthe current for operating the relay mechanism and tripping the circuitbreakers has usually been derived from the main circuit by means of aseries transformer, the secondary circuit of which includa the operatingcoil of the relay, the tripping coil of the circuit breakers, and therelay contact members which normally short circuit the latter coil, butare separated to permit its energization upon the occurrence of anoverload or other predetermined circuit condition. There is usually asuflicient amount of current in this secondary circuit to cause arcingat the relay contact members, and at times it may be sufficient to causethem to weld or stick together, and the difficulty is rendered moreserious when there is slow separation of the contact members due to theemployment of a dash pot, or other retarding device,'- for introducing atime interval between the occurrence of an overload and the opening ofthe circuit breakers. Furthermore, arcing between the contact membersmay so burn and injure them as to prevent them from making goodelectrical contact w en brought into engagement.

According to my present invention I have provided a tripping device thatis supplied with energy from the main circuit, but that does not requirethe interruption of a circuit carrying an appreciable current, therebyovercoming the hereinbefore mentioned difficulties.

My invention is illustrated in the accompanying drawings, Figure 1 ofwhich diagrammatically illustrates a part of a system embodying thesame, and Figs. 2, 3, 4 and 5 respectively illustrate several differentmodificat1ons of the electromagnetic device that is employed fortripping the circuit breaker. A typical system in connection with whichprises an alternating current circuit 1 that .is adapted to beinterrupted'by means of a circuit breaker 2 and in series with oneconductor of which is the primary winding 3 of a current transformer 4,the circuit of the secondary winding 5 of which includes o ne of thewindings (3 of a relay 7 of any ordinary or suitable construction.

The relay 7, as illustrated, is of the induction type and is preferablyconstructed as set forth in application, Serial No. 497,799, filed May22, 1909, which has been assigned to applicants assignee. This relay mayarranged to close the switch actuated by it instantaneously or after atime interval, as desired. The present invention is particularly adaptedfor use with relays of this type because of their light construction andvery sensitive character, but any other suitable type of relay may beemployed if desired.

The circuit breaker 2 is adapted to be tripped by means of anelectromagnetic de vice or relay 8 that comprises a stationarymagnetizable core member 9 in the form of a hollow rectangle with a polepiece 10 extending inwardly and downwardly from the top cross piecethereof, and having a gap in the lower cross-piece between which isinter- 10 and the armature 11 are surrounded by a coil 12 which tends toraise the armature into engagement with the pole piece.

The electromagnetic device or relay as thus described is such as hasheretofore been commonly employed as a relay for tripping circuitbreakers, but its functions are modified by the use of an auxiliary corepart 13 of substantially E-shape that is mounted with its longer legsterminating adjacent to the lower end of the core member 9. The armature12 normally rests upon the middle leg or pole piece of the core part 13,and, together with the said middle leg or pole piece, is surrounded bytwo coils 14 and 15, respectively, the former of which is connected inseries with the coil 12.

The coils 12 and 14 are supplied with current from the secondary winding5 of the series transformer, and are preferably connected in series withthe coil 6 of the relay 7, though they may be connected in any othersuitable relation with respectthereto.

The coil 15 is normally open circuited, but

is adapted to be short-circuited by engagement of the contact members 16and 17 of the relay 7 under predetermined circuit conditions, such, forinstance, as upon the occurrence of an overload or of areversal of thedirection of flow of energy in the main circuit 1.

' Under normal circuit conditions,-the current in the winding 6 of therelay 7 is insuflicient to cause the switch 1617 to close,

andv consequently, the coil 15 remains opencircuited and has no effect.However, the coils 12 and 14 are continuously energized so long as thecircuit breaker 2 remains closed, but, being located upon dpposite sidesof the lower end cross-piece of'tlie core member 9, and being alsoprovided with separate magnetic circuits,..they exert opposing pullsupon the armature 11. The magnetic circuit of the coil 14 beingsubstantially closed under normal conditions, the armature re mainsstationaryv in the position shown. Also, since the magnetic circuit ofthe coil 14 is normally substantially closed, whereas, a considerableair gap exists at the upper end of the armature 11 in the magneticcircuit of the coil 12, it is obvious that the coil 14 may,and-preferably does have, a smaller number of convolutions than the coil12.

When an overload or other abnormal cond1t1on occurs upon the clrcuit 1,an increased current 'is induced in the winding 5 of the ing of theswitch being delayed or not, as

desired. When the switch 1617 is closed, the coil 15 is short circuited,and an electromotive force is induced in it by the coil 14, therebydecreasing the magnetizing effect of the coil 14 because of the counterflux produced by the coil 15. When the magnetizing effect of the coil 14is reduced, the pull exerted by the coil 12 is permitted to preominateover that of the coil 14, and the armature 11 is accordingly raised,thereby tripping the circuit breaker. Inasmuch as, under this condition,the current in the coil 12 is large as compared with its normal value,and, since the pull of the coil 14 is nearly eliminated, the armature 11is raised quickly and with considerable force, thereby insuring promptand reliable tripping of the circuit breaker. When the overload or otherabnormal circuit condition disappears, or the circuit breaker-is opened,the switch l617 is opened and the armature 11 of the relay 8 is alsoreturned by gravity to its normal position. The operations of the deviceare accordingly automatic, both with respect to the tripping of thecircuit breaker, and to resetting in their normal positions upon closingof the circuit breaker, and the restoration of normal conditions in thecircuit.

It will, of course, be understood that since the magnetic circuit of thecoil 15 is separate from that of the coil 12, the coil 15 will notmaterially afiect the pull exerted by the coil 12 upon the armature. p

The coils 12 and 14 may be oppositely wound, as shown in Fig. 1, or theymay be similarly wound, if desired, as shown in Fig. 2, it being onlyessential that they exert opposing pulls on the armature 11.

Instead of having the coil 15 normally open circuited, it may be shortcircuited through a resistance 19 as shown in Fig. 2, in which case therelay 1617 will be employed for shunting the said resistance andestablishing a. low resistance short circuit for the coil 15. With thisarrangement, the coil 12 will become sufliciently energized at a certainexcessive current value to enable it to predominate over the coil 14,even though the switch 1617 remains open, thereby raising the abnormalcircuit condition, and the tripping of the circuit breaker when theabnormal circuit condition is only slightly abnormal,

and when it is desirable to provide for instantaneous operation of thecircuit breaker :when. the abnormal condition is extreme.

The resistance 19 is variable'for thepurpose of adjusting the currentvalue at which the circuit breaker will be tripped when the abnormalcircuit condition is extreme.

Another modification that may be found useful under certain conditionsis illustrated by Fig. 3 in' which the coil 14 has been omitted and onlya single coil 20 surrounds thelower end of the armature 11, the saidcoil being supplied with current from a suitable auxiliary source ofpower 21. The

and t condition, it is open-circuited and rendered.

of no efiect, whereupon, the coil 12 raises the armature 11.

In the modification of Fig. 4, only a single coil 23 is employed at thelower end of the armature 11, and this coil is supplied wit-h currentfrom another coil 24 that surrounds one side portion of the core 9, andin which current is induced by the flux produced by the coil 12. Thecoils 23 and 24 are normally connected in a closed circuit by the switchparts 25 of a relay 26 that is here illustrated as ofthe solenoid orelectromagnet type and the operation of which is retarded by means of adash 0t 27. Under normal circuit conditions, t e current supplied to thecoil 23 from the coil 24 is suificient to retain the core 11 in itslowermost or normal position in opposition to the pull exerted by thecoil 12. However, upon the occurrence of an overload, the switch 25 ofthe relay 26 is opened, thereby rendering the coil 23 of no effect, andpermittin the coil 12 to raise the armature.

A still further modification in which only a single coil 29 is employedat the lower end of the armature 11, is shown in Fig. 5, the coil 29being, in this case, also supplied with current from a coil 30 thatsurrounds one side of the core 9. The coil 29 normally receivessuflicient current from the coil 30 to prevent the coil 12 from raisingthe core 11, but, upon the occurrence of an overload, it isshort-circuited by the switch parts 31 of a relay 32, which switch partsare normally out of engagement. Upon short CIT- cuitin coil 29, it isrendered of no effect,

he coil 12 is permitted to raise the armature 11.

I It will be observed that with all the modifications illustrated, thecurrent carried by the contact members of the relay may be small ascompared with that traversing the secondary circuit of the seriestransformer and that, therefore, no difiiculty is experienced witharcing and burning of the contact members. Furthermore, the circuitconnections are very simple and are such, in most cases, as to avoid thenecessity of employing an auxiliary source of current.

While Ihave shown and described my invention as applied to the trippingof a circuit breaker, "it may obviously be employed for other purposes,if desired, with out departing from the spirit of the invention.

I claim as my invention:

1. The combination with a relay having a winding, of an electromagnetcomprising a stationary core member, a movable core member, two windingsthat produce opposing pulls upon the movable core member and that areconnected in series relation with the winding of thesaid relay, and athird winding that is controlled by the said re ay.

2. The combination with an electromagnet comprising a stationary coremember, a movable core member, two windings adapted to produce opposingpulls upon the movable core member, and a third winding, of means forclosing the circuit of said third Winding.

3. The combination with an electromagnet comprising a stationary coremember, a movable core member, and two windings adapted to produceopposing pulls upon the said movable core member, of means forneutralizing the magnetizing effect of one of the said windings underpredetermined conditions.

4. The combination with an electromagnet comprising a stationary coremember, a movable core member, two windings adapted to produce opposingpulls upon the said movable member, of means for decreasing theefiectiveness of one of the said windings under predeterminedconditions. i

5. The combination with a relay, of an electromagnetic device comprisinga stationary'core member, a movable core member, two windings adapted tomove the movable core member in opposite directions,

and a third winding controlled by the said relay to neutralize theelfect of one of the said oppositely acting windings.

' 6. An electromagnetic device comprising a stationary magnetizablecore-member having two magnetic paths, a movable core member, a windingfor each of the magnetic paths tending to move the movable core memberin opposite directions, and a third winding for decreasing themagnetization of one of the said magnetic paths.

7. The combination with a relay having an operating winding, of anelectromagnet comprising a stationary core member, a mov-- able coremember, two oppositely acting windings therefor connected in seriesrelation with the winding of the said relay, and a third coil thecircuit of which is controlled by the relay.

8. The combination with an electrical circult, a transformer connectedto said circuit, and a relay having a winding supplied from thetransformer, of an electromagnet comprising two oppositely actingwindings that are connected in series with the relay winding, and athird winding the circuit of which is controlled by the relay.

9. The combination with an electrical circuit, a transformer connectedto said circuit, and a relay having a winding supplied from thetransformer, of an electromagnet comprising relatively movable coremembers providing two magnetic circuits, two windlngs respectlvely forsald magnetic circuits, the said windings being connected in series withthe relay winding, a normally open-circuited winding for one of saidmagnetic circuits that is short-circuited by the relay underpredetermined conditions.

10. The combination with an electromagnet comprising two normallyenergized oppositely acting windings, and a normally open-clrcuitedwinding, of means for shortcircuiting the latter winding underpredetermined conditions.

11. The combination with an electromagnet comprising relatively movablecore members providing two magnetic circuits, a single winding for oneof said circuits, and two windings for the other, one of which isnormally open-circuited, of means for shortcircuiting the latter windingunder predetermined conditions.

12. The combination with an electromagnet comprising relatively movablecore members providing two magnetic circuits, two normally energizedseries connected windings respectively for said magnetic circuits, and anormally open-circuited winding for one of said magnetic circuits, ofmeans for short-circuiting the latter winding under predetermined.conditions.

13. An electromagnet comprising an armature, a yoke surrounding thearmature and having lateral projections that extend inwardly adjacent toan intermediate portion of the armature, a winding that surrounds thearmature upon both sides of the said projections, and a winding thatsurrounds the armature upon only one side thereof;

14:. The combination with a relay, of an electromagnet comprising anarmature, a yoke surrounding the armature and having lateral projectionsthat extend inwardly adjacent to an intermediate portion of thearmature, a normally energized winding that surrounds the armature uponboth sides of the said projections, and a normally opencircuited windingthat surrounds the armature upon only one side thereof and that isshort-circuited by the relay under predetermined conditions.

1.5. An electromagnet comprising a movable armature, a normallyenergized winding tending to actuate the armature, and another windingconnected in series relation to the first mentioned winding forpreventing such actuation of thearmature except under predeterminedconditions.

16. The combination with an electromagnet comprising a movable armature,a normally energized winding tending to actuate the armature, andanother winding connected in series with the first mentioned winding fornormally preventing such actuation of the armature, of means forrendering the latter winding inefi'ective under predeterminedconditions.

17. The combination with an electromagnet comprising twoseries-con'nected normally energized oppositely acting windings, ofmeans for rendering one of said windings ineflective under predeterminedconditions. 18. The combination with an electromagnet comprising twoseries-connected oppositely acting windings, of means for rendering oneof said windings inefl'ective under predetermined conditions.

19. The combination with an electromagnet'comprising a movablearmature,a winding that normally attracts the armature to retain it in a givenposition, of means for causing the said windingto move the armature toanother position under predetermined conditions.

20. The combination with an electrical circuit, a series transformerconnected thereto, and a relay having a winding supplied from thetransformer, of an electromagnet having a main winding also suppliedfrom' an operating winding, of an electromagnet comprlsing a stationarymagnetizable core member having two magnetic paths, a movable coremember, a winding for each of the paths connected in series relation tothe winding of the relay, and a third winding the circuit of which iscontrolled by the relay. I

22. An electromagnetic device comprising a stationary magnetizable coremember hav ing two magnetic paths, a movable core member, means for soenergizing the said paths that the movable core member is nor mally heldin one position by reason of its embracing more lines of flux from onepath than from the other, and means for so neutralizing the energizationof one path that the movable core member will be moved to anotherposition under predetermined conditions.

23. The combination with an electromagnet comprising a magnetizable corehaving a divided magnetic circuit and an armature subject to theinfluence of both circuits.

ing adjacent to the aforesaid core member upon opposite sides of theopening therein.

25. An electromagnet comprising a main magnetizable core member havingsubstantially the form of a hollow rectangle and an opening in one ofits sides, an armature extending through the said opening, an auxiliarycore member having legs terminating adjacent to the aforesaid coremember upon opposite sides of the opening therein,

and windings for opposite ends of thearmature.

26. The combination with an electromagnet comprising twoseries-connected normally energized oppositely acting windings, and athird winding, of means for so controlling the circuit of the thirdwinding as to neutralize the efl'ect of one of the normally energizedwindings under predetermined conditions.

27. The combination with an electromagnet comprising twoseries-connected oppositely acting windings, and a third winding, ofmeans for so controlling the circuit of the third winding as to decreasethe effect of one of the series-connected windings under predeterminedconditions. 28. The combination with an electromagnet comprising arelatively movable core member providing two magnetic circuits, awinding that normally energizes one circuit more than the other toattract the movable core member toa predetermined position, of means forcausing the said winding to so energize the magnetic circuit as to movethe movable core member to another position under predeterminedconditions.

In testimony whereof I have hereunto subscribed my name this 30 day ofJune BENJAMIN H. SMITH. Witnesses:

QUINCY A. BRACKETT, B. B. HINES.

